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Re: CN (xDMIR) Two Harbors runaway and Orinoco brake system
Author: Anon. CN Employee from MN
Date: 01-13-2014 - 20:40
While the NTSB investigation is still active and this is in no way conclusive, there were several contributing factors in this story that are actively discussed among the crews here:
* Two Harbors Hill is 3% grade, with several knobs/"flat spots"
* Hill was not previously plowed out, rail buried under recent deep snowfall (lower wheel-rail friction).
* Temperatures were well below zero (-20?) on day of incident
* Train was delayed for nearly 2 hours getting re-crewed at the last flat spot (Waldo, MN) prior to final 3% descent into the treacherous Two Harbors Yard and Ore Docks. In this time the wheels, brake shoes, pistons and other brake components cooled off due to extreme cold temps. Once the brakes cool in that weather, it really does not matter how much air you set (at least until the brakes have been applied far enough for them to warm up and grab again).
* Train was placed into emergency almost immediately after brakes released, but speed rapidly climbed to nearly 50 MPH down the remaining segment into the Two Harbors Yard.
* Engineer on the final runaway segment of this trip had roughly 40 years experience operating on this territory.
While the NTSB will surely have much more light to shed on the incident down the road, a couple of obvious lessons to be learned in cold-weather mountain railroading:
1) ensure steep mountain grades are plowed after a significant fresh snowfall by snowfighting equipment (plows, flangers, etc.) rather than by the next train
2) don't stop a train for an extended time period in the middle of a mountain grade descent in extreme cold weather for something predictable and avoidable, such as a planned recrew.
* Two Harbors Hill is 3% grade, with several knobs/"flat spots"
* Hill was not previously plowed out, rail buried under recent deep snowfall (lower wheel-rail friction).
* Temperatures were well below zero (-20?) on day of incident
* Train was delayed for nearly 2 hours getting re-crewed at the last flat spot (Waldo, MN) prior to final 3% descent into the treacherous Two Harbors Yard and Ore Docks. In this time the wheels, brake shoes, pistons and other brake components cooled off due to extreme cold temps. Once the brakes cool in that weather, it really does not matter how much air you set (at least until the brakes have been applied far enough for them to warm up and grab again).
* Train was placed into emergency almost immediately after brakes released, but speed rapidly climbed to nearly 50 MPH down the remaining segment into the Two Harbors Yard.
* Engineer on the final runaway segment of this trip had roughly 40 years experience operating on this territory.
While the NTSB will surely have much more light to shed on the incident down the road, a couple of obvious lessons to be learned in cold-weather mountain railroading:
1) ensure steep mountain grades are plowed after a significant fresh snowfall by snowfighting equipment (plows, flangers, etc.) rather than by the next train
2) don't stop a train for an extended time period in the middle of a mountain grade descent in extreme cold weather for something predictable and avoidable, such as a planned recrew.
